Combination cancer therapy using chk inhibitor

ABSTRACT

Disclosed is the use of a checkpoint kinase (CHK) inhibitor in combination with i) an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting/sustaining molecule, and optionally ii) a chemotherapeutic agent such as gemcitabine, in cancer treatment.

RELATED APPLICATIONS AND INCORPORATION BY REFERENCE

This application claims priority to U.S. provisional application No. 62/957,806 filed on Jan. 7, 2020.

The foregoing application, and all documents cited therein or during its prosecution (“appln cited documents”) and all documents cited or referenced herein (including without limitation all literature documents, patents, published patent applications cited herein) (“herein cited documents”), and all documents cited or referenced in herein cited documents, together with any manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention. More specifically, all referenced documents are incorporated by reference to the same extent as if each individual document was specifically and individually indicated to be incorporated by reference. Any Genbank sequences mentioned in this disclosure are incorporated by reference with the Genbank sequence to be that of the earliest effective filing date of this disclosure.

TECHNICAL FIELD

The present disclosure relates to the use of a checkpoint kinase (CHK) inhibitor in combination with an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting/sustaining molecule, and optionally an additional chemotherapeutic agent in cancer treatment.

BACKGROUND OF THE INVENTION

Cancer is the second leading cause of deaths globally, and the average 5-year survival rates for adult patients are quite low, about 14-56% in North American.

The current options for cancer treatment traditionally included surgery, radiation therapy, chemotherapy, hormone therapy, and immunotherapy. Radiation therapy and chemotherapy remain first-line treatments for various types of cancers due to efficient destruction of cancer cells. However, these two commonly adopted therapies are toxic to patients as they usually non-selectively destroy healthy cells and cause depression of the immune system. Cancer immunotherapy involves activation of the immune system and amplification of immune responses, and was voted “breakthrough of the year” by Science in 2013. It offers an option of lesser high-grade toxicity compared with other stand therapies, and has enjoyed an unparalleled success over its peers. However, a significant subset of patients do not respond to immunotherapy as a monotherapy, probably because cancer cells develop several mechanisms to evade immune surveillance and induce immune tolerance. Targeted therapy is a medical treatment that partly overlaps the chemotherapy and immunotherapy where chemotherapeutic agents or biopharmaceuticals interfere with specific targeted molecules needed for carcinogenesis and tumor growth or tissue environment contributing to cancer growth and survival, and is sometimes less harmful to healthy cells than the traditional cytotoxic chemotherapy.

Combination therapy has emerged as a promising new cancer treatment strategy, as the combination of two or more therapeutic treatments may target more than one cancer-inducing or sustaining pathways so as to increase the chance of killing cancer cells and to minimize drug resistance.

For example, low-dose gemcitabine (LDG) is currently tested in clinical trials with several small molecule inhibitors of checkpoint kinase 1 (CHK1). Moreover, based on favorable clinical outcome, U.S. Food and Drug Administration approved two chemotherapy medications, carboplatin and etoposide, in combination with an immunotherapeutic agent atezolizumab for the frontline treatment of extensive stage small cell lung cancer (SCLC). The need to better understand the extent to which chemotherapy may enhance immune-checkpoint blockade (ICB) response has thus been recognized by researchers, and new approaches beyond cytotoxic chemotherapy which may represent more optimal treatment regimen(s) for immunotherapy combinations have been explored.

Checkpoint Kinase

In eukaryotic cells, the cell cycle is regulated by checkpoints that control the transition from one phase to another. The transition through the S and G2/M phase is regulated by checkpoint kinase 1 (CHK1) and, at a lower rate, by checkpoint kinase 2 (CHK2).

The checkpoint kinases are the regulator of DNA replication and DNA damage response (DDR). In particular, studies have shown CHK1 is the master regulator of replication stress (RS) which is characterized by slowing or stalling of the replication fork and mainly caused by DNA damage, replication-transcription collision, and depletion of deoxyribonucleoside triphosphate (dNTP) pools. RS may lead to genome instability and is therefore linked with cancer cells. CHK1, in response to the RS, temporarily arrests the cell cycle and manages replication origin firing, preventing excessive DNA damage and increasing the overall survival fitness of the tumor cells (Kotsantis P, Petermann E, Boulton S J. Mechanisms of oncogene-induced replication stress: jigsaw falling into place. Cancer Discov. 2018. 8:537-555).

High expression of CHK1, along with other DDR proteins, is observed in certain cancers such as SCLC (Byers L A et al. Proteomic profiling identifies dysregulated pathways in small cell lung cancer and novel therapeutic targets including PARP1. Cancer Discov. 2012. 2:798-811; Sen T et al. CHK1 inhibition in small cell lung cancer produces single-agent activity in biomarker-defined disease subsets and combination activity with cisplatin or olaparib. Cancer Res. 2017. 77:3870-3884), and inhibition of CHK1 expression may increase the sensitivity of cancer cells to DNA damage therapy, reversing drug resistance or tolerance of cancer cells.

Combination Therapy Using CHK Inhibitor

Despite of its promising anti-tumor effects, the CHK1 inhibitor may adversely affect DNA damage repair in healthy cells and may suppress the immune system to some extent. One possible way to reduce the harm to human body while keeping the anti-tumor effect is to find a combination regimen where the CHK inhibitor works with another agent synergistically to provide a better anti-tumor therapy using a lower dose of the CHK inhibitor.

The candidate agent to be administered with the CHK inhibitor may be an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting/sustaining molecule, such as a PD-1/PD-L1 inhibitor, a CTLA-4 inhibitor, or an ErbB2 inhibitor. The CHK inhibitor may be also used in combination with a chemotherapeutic agent such as gemcitabine.

Gemcitabine is known to cause dNTP depletion and fork stalling, even at sub-therapeutic concentrations. The combination of LDG with CHK1 inhibitors represents a unique approach to combining chemotherapy with targeted agents. Instead of using standard-dose chemotherapy to induce cancer cell death, the LDG is used for its RS-inducing properties to increase reliance of cancer cells on CHK1 and therefore potentiate the CHK1 inhibitor's intrinsic cytotoxicity and immunostimulatory activities.

CHK1 and DDR inhibition was further demonstrated to synergize with anti-PD-L1 in vivo (Sen T et al. supra; Harding S M et al. Mitotic progression following DNA damage enables pattern recognition within micronuclei. Nature. 2017. 548:466-470; Jiao S et al. PARP inhibitor upregulates PD-L1 expression and enhances cancer-associated immunosuppression. Clin Cancer Res. 2017. 23:3711-3720). Very recently, Sen et al. found that the combined treatment of SRA737 (an oral small molecule inhibitor of CHK1) and anti-PD-L1 leads to an antitumor response in multiple cancer models, and combining LDG with SRA737 and anti-PD-L1/anti-PD-1 significantly increased anti-tumorigenic CD8+ cytotoxic T cells, dendritic cells, and M1 macrophage populations in an SCLC model (Triparna Sen et al., SRA737, and Low-Dose Gemcitabine Enhances the Effect of Programmed Death Ligand 1 Blockade by Modulating the Immune Microenvironment in SCLC. Journal of Thoracic Oncology. 2019. 14(12): 2152-2163).

Although encouraging data have been obtained in several combination therapies, it should be noted that not all therapies or specific agents can be combined and even fewer combination treatments work in a synergistic manner. One therapeutic agent may change a secondary agent's pharmacology and thus disable its anti-tumor activity. For example, one therapeutic agent may change the conformation, or inhibit the metabolism of a secondary agent in human body, leading to the buildup of toxicity. For example, in a pooled analysis of 14 phase I-III studies, while 64% of patients receiving various doses of ipilimumab (anti-CTLA-4) experienced immune-related adverse effects, patients receiving dual therapy with anti-PD-1 mAb plus ipilimumab had a 93% incidence of adverse events (Wolchok, J. D., et al., Nivolumab plus ipilimumab in advanced melanoma. N. Engl. J. Med., 2013. 369: 122-33). Full investigation is thus needed on the interaction between two or more anti-tumor agents in a combination regimen before coming to a conclusion that whether the combination regimen is proper or not, or whether a maximum efficacy may be achieved with minimal toxicity.

SUMMARY OF THE INVENTION

The present inventor has surprisingly found that the compounds disclosed in WO2009/092278 and WO2011/035077 as the CHK inhibitors may work synergistically with an anti-PD-1 antibody to provide an enhanced anti-tumor effect with not elevated toxicity, suggesting this CHK inhibitor may be used in combination with an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting/sustaining molecule in cancer treatments.

The present inventor further surprisingly found that such a checkpoint kinase inhibitor may work synergistically with an anti-PD-1 antibody and a chemotherapeutic agent, such as gemcitabine, to provide a further enhanced anti-tumor effect without elevated toxicity, suggesting this inhibitor may be used in combination with i) an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting molecule, and ii) a chemotherapeutic agent in cancer treatment.

Therefore, in a first aspect, the present disclosure discloses a method for treating a cancer, comprising administering a subject in need thereof a therapeutically effective amount of a compound of formula I, or the pharmaceutically acceptable salt thereof, in combination with an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting/sustaining molecule,

-   -   wherein Y is NH, O, S or CH₂;     -   R¹ is selected from the group consisting of:

-   -   wherein X is CH₂, NH, S, or O,     -   R⁸=—H, —NH₂, —OH, —N(R⁴R⁵), —C(R⁴R⁵)₁₋₇NR⁶R⁷, —C(R⁴R⁵)₁₋₇OR⁶, or         —N(R⁴)NR⁵R⁶, wherein R⁴, R⁵, R⁶, and R⁷ are independently H,         C₁-C₆ alkyl, C₃-C₈ cycloalkyl with or without nuclear         heteroatoms such as O, S, and N; optionally substituted aryl, or         optionally substituted heteroaromatic,     -   R⁹, R¹⁰, R¹¹, R¹², and R¹³ are independently H, C₁-C₆ alkyl,         C₃-C₈ cycloalkyl with or without nuclear heteroatoms such as O,         S or N; optionally substituted aryl, or optionally substituted         heteroaromatic,     -   R² is selected from a group consisting of H, OH, NH₂, OR¹⁴,         NR¹⁴R¹⁵, alkyl, aryl, heteroaryl, cycloalkyl, arylalkyl,         heterocyclyl, heterocyclylalkyl, alkenyl, and alkynyl, wherein         R¹⁴ and R¹⁵ are independently H, C₁-C₆ alkyl, C₃-C₈ cycloalkyl         with or without nuclear heteroatoms such as O, S, N; optionally         substituted aryl, or optionally substituted heteroaromatic, and     -   R³ is selected from a group consisting of H, alkyl, aryl,         heteroaryl, cycloalkyl, arylalkyl, heterocyclyl,         heterocyclylalkyl, alkenyl, and alkynyl.

In One embodiment, R³ is selected from the group consisting of

-   -   wherein R¹⁶, R¹⁷, and R¹⁸ are independently H; F, Cl, Br, I;         C₃₋₈cycloalkyl with or without or with substitutions, wherein a         substitution is selected from the group consisting of         C₁-C₈alkyls, C₃-C₈ cycloalkyls, aryls, and heteroaryls; —OR¹⁹;         —SR¹⁹; —NR¹⁹R²⁰; —S(O)R¹⁹; —S(O)₂R¹⁹; —S(O)₂NR¹⁹R²⁰;         —C(O)NR¹⁹R²⁰; —N(R¹⁹)C(O)R²⁰; —N(R¹⁹)S(O)₂R²⁰;         —N(R¹⁹)C(O)N(R²⁰R²¹); N(R¹⁹)C(O)OR²⁰; optionally substituted         aryl, optionally substituted heteroaryl, optionally substituted         aryalkyl, optionally substituted heterocyclyl, optionally         substituted heteterocyclylalkyl; optionally substituted alkenyl,         or optionally substituted alkynyl;     -   where R¹⁹, R²⁰, and R²¹ are independently H, C₁-C₈ alkyl, C₃-C₈         cycloalkyl, optionally substituted aryl, optionally substituted         alkylaryl, or optionally substituted heteroaryl,     -   or R¹⁶, R¹⁷, and R²¹ are independently part of a fused ring         containing 0-3 heteroatoms selected from N, O, and S.

In one embodiment, Y is NH. In one embodiment, Y is O. In one embodiment, Y is S.

In one embodiment, the compound of formula I is selected from the group consisting of

-   2-(4-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(2-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(2-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(S-3-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(R-3-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-piperidine-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-piperidine-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxyli-c     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(2-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(S-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(R-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(2-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide -   2-(4-chlorophenyl)-4-(4-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide -   2-(4-chlorophenyl)-4-(S-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(R-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-fluorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-bromophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(2-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(S-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(R-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-piperibine-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(2-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(S-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(R-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(2-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(4-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(S-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(R-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-bromophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(2-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(S-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(R-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic     acid amide, -   2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-piperidinyloxy)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide, -   2-(3-fluorophenyl)-4-(3-piperidinylthio)-thieno[2,3-d]pyridazine-7-carboxylic     acid amide,2-(4-fluorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-tetrahy     dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-tetrahydropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(2-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(4-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(S-3-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(R-3-piperidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno     [2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahy     dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahy     dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-tetrahy     drofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(S-3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(R-3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; -   2-(4-chlorophenyl)-4-(3-tetrahy     drofuranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; -   2-(4-fluorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(2-pyridinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(4-pyridinemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; -   2-(4-chlorophenyl)-4-(3-thiopyranylmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-thiopyranylmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; -   2-(4-chlorophenyl)-4-(3-pyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-pyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; -   2-(4-fluorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-furanmethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-fluorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-bromophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(2-pyrrolemethyl)-thieno[2,3-d]     pyridazinyl-7-formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; -   2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; -   2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl     formamide; -   2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl     formamide; and -   2-(3,5-dichlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide.

In one embodiment, the compound is selected from the group consisting of 2-(3-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-piperidinyloxy)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-piperidinylthio)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, and 2-(3,5-dichlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide.

The immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule may be an inhibitor of PD-1, PD-L1, CTLA-4, HER-2, CD20, CD33, or CD52. In embodiments, the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule may be an antibody targeting PD-1, PD-L1, CTLA4, HER-2, CD20, CD33, and/or CD52, and an antibody-drug conjugate (ADC) or a CAR-T cell targeting PD-L1, HER-2, CD20, CD33, and/or CD52.

In one embodiment, the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule is a PD-1 inhibitor, such as an anti-PD-1 antibody; or a PD-L1 inhibitor such as an anti-PD-L1 antibody. The anti-PD-1 antibody can be Nivolumab, Pembrolizumab, or Toripalimab. The anti-PD-L1 antibody may be Atezolizumab, Druvalumab or Avelumab.

The CTLA-4 inhibitor may be an anti-CTLA-4 antibody, such as Ipilimumab. The anti-HER2 antibody may be Trastuzumab or Pertuzumab. The anti-CD-20 antibody is Rituximab, Ibritumomab, Tiuxetan, Tositumomab, Ofatumumab, Ocrelizumab, Veituzumab or Obinutuzumab. The anti-CD-33 antibody may be Gemtuzumab. The anti-CD-52 antibody may be Alemtuzumab.

In one embodiment, the cancer is a solid cancer selected from the group consisting of lung, prostate, ovarian, brain, breast, skin, bladder, colon, gastrointestinal, head and neck, gastric, pancreas, neurologic, renal, and liver cancer. In one embodiment, the cancer is colon cancer. In one embodiment, the cancer is colon adenocarcinoma.

In one embodiment, the cancer is a hematological cancer selected from the group consisting of lymphocytic leukemia, myeloid leukemia, non-Hodgkin lymphoma, and Hodgkin lymphoma.

The compound of formula I and the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule may be administered concurrently as a single composition in a pharmaceutically acceptable carrier, or concurrently as separate compositions. They can also be administered sequentially.

The present disclosure also discloses the use of the compound of formula I in combination with the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule in treatment of a cancer disease.

The exemplary combined use provides an enhanced anti-tumor effect as compared to either monotherapy, with equal or even slightly reduced toxicity, which was validated in a mPD-1^(−/−) mPD-L1^(−/−)hPD-1^(+/+)hPD-L1^(+/+) transgenic mouse model.

The CHK1 inhibitor of the present disclosure, even at a dose that shows no anti-tumor effect alone, works synergistically with an anti-PD-1 antibody.

In a second aspect, the present disclosure discloses a method for treating a cancer, comprising administering a subject in need thereof a therapeutically effective amount of a compound of formula I, or the pharmaceutically acceptable salt thereof, in combination with i) an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting molecule, and ii) a chemotherapeutic agent.

The immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule may be an inhibitor of PD-1, PD-L1, CTLA-4, HER-2, CD20, CD33, or CD52. In embodiments, the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule may be an antibody targeting PD-1, PD-L1, CTLA4, HER-2, CD20, CD33, and/or CD52, and an antibody-drug conjugate (ADC) or a CAR-T cell targeting PD-L1, HER-2, CD20, CD33, and/or CD52.

In one embodiment, the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting/sustaining molecule is a PD-1 inhibitor, such as an anti-PD-1 antibody; or a PD-L1 inhibitor such as an anti-PD-L1 antibody. The anti-PD-1 antibody can be Nivolumab, Pembrolizumab, or Toripalimab. The anti-PD-L1 antibody may be Atezolizumab, Druvalumab or Avelumab.

The CTLA-4 inhibitor may be an anti-CTLA-4 antibody, such as Ipilimumab. The anti-HER2 antibody may be Trastuzumab or Pertuzumab. The anti-CD-20 antibody is Rituximab, Ibritumomab, Tiuxetan, Tositumomab, Ofatumumab, Ocrelizumab, Veituzumab or Obinutuzumab. The anti-CD-33 antibody may be Gemtuzumab. The anti-CD-52 antibody may be Alemtuzumab.

The chemotherapeutic agent suitable for the present invention may be cisplatin, pemetrexed, gemcitabine, cytarabine, hydroxycarbamide, temozolomide, irinotecan, cyclophosphamide, mitoxantrone, etoposide, folinic acid, fludarabine, fluorouracil, or a combination thereof.

In one embodiment, the cancer is a solid cancer selected from the group consisting of lung, prostate, ovarian, brain, breast, skin, bladder, colon, gastrointestinal, head and neck, gastric, pancreas, neurologic, renal, and liver cancer. In one embodiment, the cancer disease is colon cancer. In one embodiment, the cancer is colon adenocarcinoma.

In one embodiment, the cancer is a hematological cancer selected from the group consisting of lymphocytic leukemia, myeloid leukemia, non-Hodgkin lymphoma, and Hodgkin lymphoma.

The compound of formula I, the immunotherapeutic agent (or the therapeutic agent targeting a cancer-promoting molecule) and the chemotherapeutic agent may be administered concurrently as a single composition in a pharmaceutically acceptable carrier, or concurrently as separate compositions. They can also be administered sequentially.

The present disclosure also discloses the use of the compound of formula I in combination with the immunotherapeutic agent (or the therapeutic agent targeting a cancer-promoting molecule) and the chemotherapeutic agent in treatment of a cancer disease.

The exemplary combined use provides an enhanced anti-tumor effect as compared to either monotherapy, with equal or even reduced toxicity, which was validated in a mPD-1^(−/−)mPD-L1^(−/−)hPD-1^(+/+)hPD-L1^(+/+) transgenic mouse model.

The CHK1 inhibitor of the present disclosure, even at a dose that shows no anti-tumor effect alone, works synergistically with an anti-PD-1 antibody and a chemotherapeutic agent.

Other features and advantages of the instant disclosure, literally described and their equivalents understood by those ordinarily skilled in the art, will be apparent from the following drawings, detailed description and examples, as well as claims, which should not be construed as limiting. The contents of all publications, references, Genbank entries, patents and published patent applications cited throughout this application are expressly incorporated herein by reference.

DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings.

FIG. 1 is a line graph showing the mice body weight change during the test.

FIG. 2 is a line graph showing the tumor size change during the test.

FIG. 3 is a photo of tumors isolated from mice at Day 27.

FIG. 4 is a line graph showing the mice body weight change during the test.

FIG. 5 is a line graph showing the tumor size change during the test.

FIG. 6 shows individual tumor sizes in mice of different groups during the test.

FIG. 7 is a dot graph showing individual tumor sizes on Day 14.

FIG. 8 is a photo of tumors isolated from mice of Group 3 and Group 4 on Day 21.

FIG. 9 is a line graph showing the tumor size change during the test.

FIG. 10 is a line graph showing the tumor size change during the test.

DETAILED DESCRIPTION OF THE INVENTION

Before particular embodiments of the present disclosure are disclosed and described, it is to be understood that this disclosure is not limited to the particular process and materials disclosed herein as such may vary to some degree. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only and is not intended to be limiting, as the scope of the present disclosure will be defined only by the appended claims and equivalents thereof.

The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Unless otherwise indicated, any heteroatom with unsatisfied valences is assumed to have hydrogen atoms sufficient to satisfy the valences.

Throughout the specification and the appended claims, a given chemical formula or name shall encompass all stereo and optical isomers and racemates thereof where such isomers exist. Unless otherwise indicated, all chiral (enantiomeric and diastereomeric) and racemic forms are within the scope of the disclosure. Many geometric isomers of C═C double bonds, C═N double bonds, ring systems, and the like can also be present in the compounds, and all such stable isomers are contemplated in the present disclosure. Cis- and trans- (or E- and Z-) geometric isomers of the compounds of the present disclosure are described and may be isolated as a mixture of isomers or as separated isomeric forms. The present compounds can be isolated in optically active or racemic forms. Optically active forms may be prepared by resolution of racemic forms or by synthesis from optically active starting materials. All processes used to prepare compounds of the present disclosure and intermediates made therein are considered to be part of the present disclosure. When enantiomeric or diastereomeric products are prepared, they may be separated by conventional methods, for example, by chromatography or fractional crystallization. Depending on the process conditions the end products of the present disclosure are obtained either in free (neutral) or salt form. Both the free form and the salts of these end products are within the scope of the disclosure. If so desired, one form of a compound may be converted into another form. A free base or acid may be converted into a salt; a salt may be converted into the free compound or another salt; a mixture of isomeric compounds of the present disclosure may be separated into the individual isomers. Compounds of the present disclosure, free form and salts thereof, may exist in multiple tautomeric forms, in which hydrogen atoms are transposed to other parts of the molecules and the chemical bonds between the atoms of the molecules are consequently rearranged. It should be understood that all tautomeric forms, insofar as they may exist, are included within the disclosure.

As referred to herein, the term “substituted” means that at least one hydrogen atom is replaced with a non-hydrogen group, provided that normal valencies are maintained and that the substitution results in a stable compound.

When a substituent is noted as “optionally substituted”, the substituents are selected from, for example, substituents such as alkyl, cycloalkyl, aryl, heterocyclo, halo, hydroxy, alkoxy, oxo, alkanoyl, aryloxy, alkanoyloxy, amino, alkylamino, arylamino, arylalkylamino, disubstituted amines in which the 2 amino substituents are selected from alkyl, aryl or arylalkyl; alkanoylamino, aroylamino, aralkanoylamino, substituted alkanoylamino, substituted arylamino, substituted aralkanoylamino, thiol, alkylthio, arylthio, arylalkylthio, alkylthiono, arylthiono, arylalkylthiono, alkylsulfonyl, arylsulfonyl, arylalkylsulfonyl, sulfonamido, e.g. —SO₂NH₂, substituted sulfonamido, nitro, cyano, carboxy, carbamyl, e.g. —CONH₂, substituted carbamyl e.g. —CONHalkyl, —CONHaryl, —CONHarylalkyl or cases where there are two substituents on the nitrogen selected from alkyl, aryl or arylalkyl; alkoxycarbonyl, aryl, substituted aryl, guanidino, heterocyclyl, e.g., indolyl, imidazolyl, furyl, thienyl, thiazolyl, pyrrolidyl, pyridyl, pyrimidyl, pyrrolidinyl, piperidinyl, morpholinyl, piperazinyl, homopiperazinyl and the like, and substituted heterocyclyl, unless otherwise defined.

As used herein, the term “alkyl” or “alkylene” is intended to include both branched and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms. For example, “C₁-C₆ alkyl” denotes alkyl having 1 to 6 carbon atoms. Exemplary alkyl groups include, but are not limited to, methyl (Me), ethyl (Et), propyl (e.g., n-propyl and isopropyl), butyl (e.g., n-butyl, isobutyl, t-butyl), and pentyl (e.g., n-pentyl, isopentyl, neopentyl).

The term “alkenyl” denotes a straight- or branch-chained hydrocarbon radical containing one or more double bonds and typically from 2 to 20 carbon atoms in length. For example, “C₂-C₈ alkenyl” contains from two to eight carbon atoms. Alkenyl groups include, but are not limited to, for example, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, heptenyl, octenyl and the like.

The term “alkynyl” denotes a straight- or branch-chained hydrocarbon radical containing one or more triple bonds and typically from 2 to 20 carbon atoms in length. For example, “C₂-C₈ alkenyl” contains from two to eight carbon atoms. Representative alkynyl groups include, but are not limited to, for example, ethynyl, 1-propynyl, 1-butynyl, heptynyl, octynyl and the like.

The term “alkoxy” or “alkyloxy” refers to an —O-alkyl group. “C₁-C₆ alkoxy” (or alkyloxy), is intended to include C₁, C₂, C₃, C₄, C₅, and C alkoxy groups. Exemplary alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy (e.g., n-propoxy and isopropoxy), and t-butoxy. Similarly, “alkylthio” or “thioalkoxy” represents an alkyl group as defined above with the indicated number of carbon atoms attached through a sulphur bridge; for example methyl-S- and ethyl-S-.

The term “aryl”, either alone or as part of a larger moiety such as “aralkyl”, “aralkoxy”, or aryloxyalkyl”, refers to monocyclic, bicyclic and tricyclic ring systems having a total of five to 15 ring members, wherein at least one ring in the system is aromatic and wherein each ring in the system contains three to seven ring members. In certain embodiments of the disclosure, “aryl” refers to an aromatic ring system which includes, but not limited to phenyl, biphenyl, indanyl, 1-naphthyl, 2-naphthyl and terahydronaphthyl.

The term “aralkyl” or “arylalkyl” refers to an alkyl residue attached to an aryl ring. Non-limiting examples include benzyl, phenethyl and the like. The fused aryls may be connected to another group either at a suitable position on the cycloalkyl ring or the aromatic ring. For example:

Arrowed lines drawn from the ring system indicate that the bond may be attached to any of the suitable ring atoms.

The term “cycloalkyl” refers to cyclized alkyl groups. C₃-C₆ cycloalkyl is intended to include C₃, C₄, C₅, and C₆ cycloalkyl groups. Exemplary cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and norbornyl. Branched cycloalkyl groups such as 1-methylcyclopropyl and 2-methylcyclopropyl are included in the definition of “cycloalkyl”. The term “cycloalkenyl” refers to cyclized alkenyl groups. C₄₋₆ cycloalkenyl is intended to include C₄, C₅, and C₆ cycloalkenyl groups. Exemplary cycloalkenyl groups include, but are not limited to, cyclobutenyl, cyclopentenyl, and cyclohexenyl.

As used herein, the term “heterocycle,” “heterocyclyl,” or “heterocyclic group” is intended to mean a stable 4-, 5-, or 6-membered monocyclic that is saturated, partially unsaturated, or fully unsaturated, and that contains carbon atoms and 1, 2, 3 or 4 nitrogen, oxygen or other non-carbon atoms.

In cases wherein there are nitrogen atoms (e.g., amines) on compounds of the present disclosure, these may be converted to N-oxides by treatment with an oxidizing agent (e.g., mCPBA and/or hydrogen peroxides) to afford other compounds of this disclosure. Thus, shown and claimed nitrogen atoms are considered to cover both the shown nitrogen and its N-oxide (N->0) derivative.

When any variable occurs more than one time in any constituent or formula for a compound, its definition at each occurrence is independent of its definition at every other occurrence. Thus, for example, if a group is shown to be substituted with 0-3 R, then said group may optionally be substituted with up to three R groups, and at each occurrence R is selected independently from the definition of R. Also, combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

When a bond to a substituent is shown to cross a bond connecting two atoms in a ring, then such substituent may be bonded to any atom on the ring. When a substituent is listed without indicating the atom in which such substituent is bonded to the rest of the compound of a given formula, then such substituent may be bonded via any atom in such substituent. Combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms that are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, and/or other problem or complication, commensurate with a reasonable benefit/risk ratio. As used herein, “pharmaceutically acceptable salts” refer to derivatives of the disclosed compounds wherein the parent compound is modified by making acid or base salts thereof. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic groups such as amines; and alkali or organic salts of acidic groups such as carboxylic acids. The pharmaceutically acceptable salts include the conventional non-toxic salts or the quaternary ammonium salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. For example, such conventional non-toxic salts include those derived from inorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, and nitric; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, 2-acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, and isethionic, and the like.

The pharmaceutically acceptable salts of the present invention can be synthesized from the parent compound that contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile are preferred. Lists of suitable salts are found in Remington: The Science and Practice of Pharmacy, 22nd Edition, Allen, L. V. Jr., Ed.; Pharmaceutical Press, London, UK (2012), the disclosure of which is hereby incorporated by reference.

As used herein, the term “effective amount” means that amount of a drug or pharmaceutical agent, i.e., a compound of the disclosure, that will elicit the biological or medical response of a tissue, system, animal or human that is being sought, for instance, by a researcher or clinician. Furthermore, the term “therapeutically effective amount” means any amount which, as compared to a corresponding subject who has not received such amount, results in improved treatment, healing, prevention, or amelioration of a disease, disorder, or side effect, or a decrease in the rate of advancement of a disease or disorder. An effective amount can be administered in one or more administrations, applications or dosages and is not intended to be limited to a particular formulation or administration route. The term also includes within its scope amounts effective to enhance normal physiological function.

The term “subject” includes any human or nonhuman animal. The term “nonhuman animal” includes all vertebrates, e.g., mammals and non-mammals, such as non-human primates, sheep, dogs, cats, cows, horses, chickens, amphibians, and reptiles, although mammals are preferred, such as non-human primates, sheep, dogs, cats, cows and horses.

As used herein, the term “treating” includes any effect, e.g., lessening, reducing, modulating, ameliorating or eliminating, that results in the improvement of the condition, disease, disorder, and the like, or ameliorating a symptom thereof.

As used herein, the term “pharmaceutical composition” refers to the combination of an active agent with a carrier, inert or active, making the composition especially suitable for diagnostic or therapeutic use in vivo or ex vivo.

As used herein, the term “parenteral” includes subcutaneous, intradermal, intravenous, intramuscular, intraarticular, intraarterial, synovial, intrasternal, intracranial, intramuscular or infusion.

Compound of Formula I

The compounds of formula I are disclosed in WO2009/092278 and WO2011/035077 as CHK inhibitors. They have direct anti-tumor effects and can sensitize other DNA-damaging drugs. The synthesis scheme and the function tests of these compounds are also specifically described in the two international patent applications.

The exemplary compounds include

(2-(3-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, referred to as Compound 6 in Examples 1 to 5),

2 (2-(3-fluorophenyl)-4-(3-piperidinyloxy)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, referred to as Compound 6-1 in Example 2),

(2-(3-fluorophenyl)-4-(3-piperidinylthio)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, referred to as Compound 6-2 in Example 2),

(2-(3,5-dichlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide, referred to as Compound 6-3 in Example 2).

Immunotherapeutic Agent or Therapeutic Agent Targeting Cancer-Promoting Molecule

The immunotherapeutic agent herein refers to a therapeutic agent involved in activation of immune system and/or amplification of immune responses. The immunotherapeutic agent includes, but not limited to, a PD-1 inhibitor, a PD-L1 inhibitor, a CTLA-4 inhibitor, and a CD33 inhibitor. The PD-1 inhibitor, PD-L1 inhibitor, CTLA-4 inhibitor, and CD33 inhibitor include, but not limited to, an anti-PD-1 antibody, an anti-PD-L1 antibody, an anti-CTLA-4 antibody, an anti-CD33 antibody, an anti-PD-L1-antibody-drug conjugate, an anti-CD33-antibody-drug conjugate, a CAR-T cell targeting PD-L1, and a CAR-T cell targeting CD33.

The therapeutic agent targeting a cancer-promoting molecule herein refers to a therapeutic agent targeting a molecule required for cancer cell growth, and partly overlaps the immunotherapeutic agent. Such an agent includes, but not limited to, a PD-1 inhibitor, a PD-L1 inhibitor, a CTLA-4 inhibitor, a HER-2 inhibitor, a CD20 inhibitor, a CD33 inhibitor, or a CD52 inhibitor. These inhibitors may be an antibody targeting PD-1, PD-L1, CTLA-4, HER-2, CD20, and/or CD33, an antibody-drug conjugate or a CAR-T cell targeting PD-L1, HER-2, CD20, and/or CD33.

Among these targets, PD-1, PD-L1 and CTLA-4 are immune checkpoints.

PD-1 is a protein found on the surface of cells that has a role in regulating the immune system's response to the cells of the human body by down-regulating the immune system and promoting self-tolerance by suppressing T cell inflammatory activity. PD-1 binds two ligands, PD-L1 and PD-L2. The binding of PD-L1 to PD-1 transmits an inhibitory signal that reduces the proliferation of antigen-specific T-cells in lymph nodes, while simultaneously reducing apoptosis in regulatory T cells (anti-inflammatory, suppressive T cells). PD-1 and PD-L1 inhibitors activate the immune system to attack tumors and are used to treat certain types of cancer, and have been one of the most intensively researched cancer therapeutics. However, only less than about 20% of patients respond PD-1/PD-L1 inhibitors.

CTLA-4, also known as cytotoxic T-lymphocyte antigen 4, is a trans-membrane protein found on the surface of T cells, which, when bound to B7 on antigen-presenting cells, prevents T cell activation. This is thought to occur during the immune system's “priming” phase in lymph nodes. The overall effect is immune down-regulation. Thus, CTLA-4 is described as an immune checkpoint “off switch.” Two fully human anti-CTLA-4 monoclonal antibodies have been developed and tested in phase III clinical trials for the treatment of patients with metastatic melanoma: Ipilimumab and Tremelimumab.

Ipilimumab has been FDA-approved for the treatment of metastatic melanoma, adjuvant melanoma, and renal cell carcinoma.

The other targets are known for their roles in promoting cancer generation and development.

The PD-1 inhibitors useful in the present invention include, but not limited to, nivolumab, pembrolizumab, cemiplimab-rwlc, toripalimab, sintilimab, camrelizumab and tislelizumab.

The PD-L1 inhibitors that can be used in the present invention include, but not limited to, atezolizumab, avelumab and durvalumab.

The CTLA-4 inhibitors that can be used in the present invention include, not limited to, ipilimumab, tremelimumab, zalifrelimab, AGEN-1181, KN-044, BCD-145, abatacept, BMS-986249, IO-102, ONC-392, REGN-4659, HBM-4003, RG 2077, and YH-001.

Certain bispecific molecules targeting PD-1 and CTLA-4 may also be used in the method of the invention, including, but not limited to, BCD-217, AK104, PSB205, and MEDI-5752.

Certain bispecific molecules targeting PD-L1 and CTLA-4 may also be used in the method of the invention, including, but not limited to, KN-046.

Chemotherapeutic Agent

The chemotherapeutic agent herein refers to a powerful chemical that kills fast-growing cells in the body. Such an agent is usually used to treat cancers, as cancer cells grow and divide faster than other cells.

Chemotherapeutic agents for cancer treatment include, but not limited to, cisplatin, pemetrexed, gemcitabine, cytarabine, hydroxycarbamide, temozolomide, irinotecan, cyclophosphamide, mitoxantrone, etoposide, folinic acid, fludarabine, and fluorouracil.

Gemcitabine, a chemotherapy medication used in treatment of a number of types of cancers, is a ribonucleotide reductase inhibitor that leads to dNTP depletion and fork stalling, blocking the formation of new DNAs. It was first approved in 1995 for medical use, and is now used as a first-line treatment alone for pancreatic cancer, and in combination with cisplatin for advanced or metastatic bladder cancer and advanced or metastatic non-small cell lung cancer. It is also used as a second-line treatment in combination with carboplatin for ovarian cancer and in combination with paclitaxel for breast cancer that is metastatic or cannot be surgically removed. Gemcitabine use may cause side effects such as bone marrow suppression, liver and kidney problems, nausea, fever, and hair loss.

Cisplatin is another chemotherapy medication commonly used in treatment of a number of cancers. It was discovered in 1845 and put into medical use in 1978. It works by binding to DNA and thus inhibiting DNA replication, and is used to treat sarcomas, SCLC, ovarian cancer and etc.

Combination Therapy

The compounds of formula I, as the CHK inhibitor, may be used in combination with i) an immunotherapeutic agent or a cancer-promoting molecule targeting therapeutic agent, and optionally (ii) a chemotherapeutic agent, to gain a better anti-cancer effect and/or a lower toxicity to human body.

The compound of formula I and the immunotherapeutic agent or the cancer-promoting/sustaining molecule targeting therapeutic agent may be administered concurrently as a single composition in a pharmaceutically acceptable carrier, or concurrently as separate compositions. They can also be administered sequentially.

In other embodiments, the compound of formula I, the chemotherapeutic agent, and the immunotherapeutic agent (or the cancer-promoting molecule targeting therapeutic agent) may be administered concurrently as a single composition in a pharmaceutically acceptable carrier, or concurrently as separate compositions. They can also be administered sequentially.

The combination therapy of the present disclosure may be used to treat a cancer, such as a solid cancer selected from the group consisting of lung, prostate, ovarian, brain, breast, skin, bladder, colon, gastrointestinal, head and neck, gastric, pancreas, neurologic, renal, and liver cancer, or a hematological cancer selected from the group consisting of lymphocytic leukemia, myeloid leukemia, non-Hodgkin lymphoma, and Hodgkin lymphoma. In one embodiment, the cancer is colon carcinoma. In one embodiment, the cancer is colon adenocarcinoma.

The combination therapy of the present disclosure may be applied to animals, preferably mammals (e.g., domesticated animals, cats, dogs, mice, rats), and more preferably humans. Any method of administration may be used to deliver the compound of formula I, the immunotherapeutic agent (or the cancer-promoting molecule targeting therapeutic agent), and/or the chemotherapeutic agent to the subject in need thereof. In certain embodiments, the compound of formula I, the chemotherapeutic agent, and/or the immunotherapeutic agent (or the cancer-promoting molecule targeting therapeutic agent) are administered orally. In other embodiments, the compound of formula I, the chemotherapeutic agent, and/or the immunotherapeutic agent (or the cancer-promoting molecule targeting therapeutic agent) are administered parenterally.

One or more additional pharmaceutical agents or treatment methods such as, for example, immune enhancers, immunosuppressants, anti-tumor vaccines, cytokine therapy (e.g., IL2 and GM-CSF), and/or tyrosine kinase inhibitors can be optionally used in combination with the combination therapy of the disclosure. The additional agents can be combined with the combination therapeutics of the disclosure in a single dosage form, or these agents can be administered simultaneously or sequentially as separate dosage forms.

Pharmaceutical Compositions and Dosing

The disclosure also provides pharmaceutically acceptable compositions which comprise a therapeutically effective amount of one or more compounds of Formula I, formulated together with one or more pharmaceutically acceptable carriers (additives) and/or diluents, a therapeutically effective amount of the immunotherapeutic agent or the cancer-promoting molecule targeting therapeutic agent mentioned above, formulated together with one or more pharmaceutically acceptable carriers (additives) and/or diluents, optionally a therapeutically effective amount of the chemotherapeutic agent mentioned above, formulated together with one or more pharmaceutically acceptable carriers (additives) and/or diluents, and optionally, one or more additional therapeutic agents if needed. The compounds of the disclosure can be administered by any suitable means, for example, orally, as tablets, capsules (each of which includes sustained release or timed release formulations), pills, powders, granules, elixirs, tinctures, suspensions (including nanosuspensions, microsuspensions, spray-dried dispersions), syrups, and emulsions; sublingually; bucally; parenterally, such as by subcutaneous, intravenous, intramuscular, or intrasternal injection, or infusion techniques (e.g., as sterile injectable aqueous or non-aqueous solutions or suspensions); nasally, including administration to the nasal membranes, such as by inhalation spray; topically, such as in the form of a cream or ointment; or rectally such as in the form of suppositories. The chemotherapeutic agent of the disclosure can be administered by any suitable means with a pharmaceutically acceptable carrier. The immunotherapeutic agent or the cancer-promoting molecule targeting therapeutic agent of the disclosure can be administered by any suitable means with a pharmaceutically acceptable carrier. The pharmaceutical composition of the present disclosure can also be prepared as liposomes and nanoparticles.

The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. A “pharmaceutically acceptable carrier” refers to media generally accepted in the art for the delivery of biologically active agents to animals, in particular, mammals, including, i.e., adjuvant, excipient or vehicle, such as diluents, preserving agents, fillers, flow regulating agents, disintegrating agents, wetting agents, emulsifying agents, suspending agents, sweetening agents, flavoring agents, perfuming agents, antibacterial agents, antifungal agents, lubricating agents and dispensing agents, depending on the nature of the mode of administration and dosage forms.

The dosage regimen for the compounds, the chemotherapeutic agent, and/or the immunotherapeutic agent or the cancer-promoting molecule targeting therapeutic agent of the disclosure will, of course, vary depending upon known factors, such as the pharmacodynamic characteristics of each particular agent and its mode and route of administration; the species, age, sex, health, medical condition, and weight of the recipient; the nature and extent of the symptoms; the kind of concurrent treatment; the frequency of treatment; the route of administration, the renal and hepatic function of the patient, and the effect desired. By way of general guidance, the daily oral dosage of each active ingredient, when used for the indicated effects, will range between about 0.001 to about 5000 mg per day, preferably between about 0.01 to about 1000 mg per day, and most preferably between about 0.1 to about 250 mg per day. Intravenously, the most preferred doses will range from about 0.01 to about 10 mg/kg/minute during a constant rate infusion.

The compound, the immunotherapeutic agent or the cancer-promoting molecule targeting therapeutic agent, and optionally the chemotherapeutic agent, of this disclosure may be administered in a single daily dose, or the total daily dosage may be administered in divided doses of two, three, or four times daily.

EXAMPLES Example 1. Combination of CHK Inhibitor and Anti-PD-1 Antibody had Synergic Anti-Tumor Effect

CT-26 WT cells were maintained at 37° C. in 5% CO₂ in RPMI 1640 medium (10-040-CV, Corning cellgro) supplemented with 10% FBS (10270-106, GIBCO) and used before the 10th subculture.

At Day 0, 45 BALB/c female mice, 4-5 weeks old, were subcutaneously injected with about 200.0 μL of the CT-26 WT cell medium containing about 5×10⁵ cells, respectively.

At Day 5, 32 tumor-bearing mice were randomly assigned to four groups according to their body weights, 8 mice per group. The remaining mice were subject to euthanasia.

The four groups of animals were administered with an anti-m-PD-1 antibody (BE0146, BioXcell) in PBS (21-040-CVR, BioXcell) at 1.0 mg/mL, Compound 6 in saline at 3.5 mg/mL, the anti-m-PD-1 antibody in combination with Compound 6, and the control vehicle (saline), respectively, at doses shown in Table 1 below.

TABLE 1 Dosing regimen Dose Group Test articles N (mg/kg) Dosing Regimen 1 vehicle 8 saline Oral administration, once per day 2 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, four times in total 3 Compound 6 8 35 Tail vein injection, once per day 4 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, four times in total Compound 6 35 Tail vein injection, once per day

Mice were observed every day for their physical conditions and activities, and mice body weight and tumor volume were measured every Tuesday, Thursday and Sunday. The tumor volume (V) was calculated as (length×width²)/2.

At Day 27, mice were subject to euthanasia, from which tumors were collected, weighed and photographed. Mice body weights, tumor sizes and tumor weights were analyzed using the t-test in SPSS, and group differences were deemed statistically significant when the p-value was 0.05 or less.

Tumor growth inhibition (TGI) was calculated by the following two formulae. Tumor growth inhibition=(average tumor size in vehicle group-average tumor size in administration group)/average tumor size in vehicle group×100% Tumor growth inhibition=(average tumor weight in vehicle group-average tumor weight in administration group)/average tumor weight in vehicle group×100%

Further, Zheng-Jun Jin's Q value was calculated using the formula Q=E_(A)+B/(E_(A)+E_(B)−E_(A)×E_(B)) to assess the combined effect of the anti-PD-1 antibody and Compound 6, wherein E_(A+B), E_(A), and E_(B) referred to the TGIs of the combination therapy, anti-PD-1 administration and Compound 6 administration, respectively. A Q value higher than 1.15 meant a synergistic or additive effect.

The animals in the vehicle group looked vigorous, and no mouse was found dead in all four groups during the experiment. The average mice body weights and average tumor sizes from Day 9 to Day 27 in different groups were shown in FIG. 1 and FIG. 2 , and the individual tumors isolated from mice at Day 27 were displayed in FIG. 3 .

As shown in FIG. 1 , the mice in each group generally had their body weights increased from Day 9 to Day 27, partly due to the tumor growth. If the tumor weight was deducted, the average mice weights in the vehicle, anti-PD-1, CHK inhibitor, and combination therapy groups were 17.71 g, 19.68 g, 18.41 g, and 18.60 g, respectively, at Day 27. It can be seen that the mice in the CHK inhibitor group or the combination group were lighter than those in the anti-PD-1 group, suggesting that the CHK inhibitor might be more toxic than the anti-PD-1 antibody, and the combination therapy did not have the toxicity increased. Actually, the mice in the combination therapy group were even slightly heavier than those in the CHK inhibitor group.

According to FIG. 2 and FIG. 3 , tumors kept growing in the vehicle group while tumor size began to decrease at Day 27 in the anti-PD-1 group, tumors in the CHK inhibitor group stopped growing since Day 15, and the tumors in the combination therapy group began to reduce at Day 15 and became significantly smaller and lighter at Day 27 than those in other groups. The tumor in one mouse of the combination group even totally vanished. All these suggested that the CHK inhibitor acted very quickly on tumors and had a very strong anti-tumor activity, and the addition of an anti-PD-1 antibody further elevated the anti-tumor effect without bringing more toxicity.

Tumor growth inhibition rates were calculated based on the tumor sizes and tumor weights at Day 27 and summarized in Table 2 below.

TABLE 2 Tumor growth inhibition rates Group TGI - TGI - Vehicle tumor size tumor weight Anti-m-PD-1 30.93% 33.23% Compound 6 72.74% 77.53% Anti-m-PD-1 + 94.34% 94.59% Compound 6

The Zheng-jun Jin's Q values based on the tumor size related TGI and tumor weight related TGI were 1.16 and 1.11, respectively, higher than or slightly lower than 1.15.

The data above indicated that 1) Compound 6, the CHK inhibitor, acted quickly on tumors with relatively strong effects; and 2) the CHK inhibitor worked synergistically with the anti-PD-1 antibody, resulting in enhanced anti-tumor effect with equal or slightly lower toxicity.

Example 2. Combination Therapy Using CHK Inhibitor at Lower Dose had Good Anti-Tumor Effect

The anti-tumor effect of Compound 6 at a lower dose in combination with an anti-PD-1 antibody was studied in this Example. Further, three compounds obtained by structurally modifying Compound 6, i.e., Compound 6-1, Compound 6-2 and Compound 6-3, were tested alone or in combination with an anti-PD-1 antibody for their anti-tumor effects.

At Day 0, 105 BALB/c female mice, 4-5 weeks old, were subcutaneously injected with about 200.0 μL of the CT-26 WT cell medium containing about 5×10⁵ cells, respectively.

At Day 5, 80 tumor-bearing mice were randomly assigned to ten groups according to their body weights, 8 mice per group. The remaining mice were subject to euthanasia.

The ten groups of animals were administered with an anti-m-PD-1 antibody (BE0146, BioXcell) in PBS (21-040-CVR, BioXcell) at 1.0 mg/mL, Compound 6 in saline at 1.5 mg/mL, Compound 6-1 in saline at 1.5 mg/mL, Compound 6-2 in saline at 1.5 mg/mL, Compound 6-3 in saline at 1.5 mg/mL, the anti-m-PD-1 antibody+Compound 6, the anti-m-PD-1 antibody+Compound 6-1, the anti-m-PD-1 antibody+Compound 6-2, the anti-m-PD-1 antibody+Compound 6-3, and the control vehicle (saline), respectively, at doses shown in Table 3 below.

Mice were observed every day for their physical conditions and activities, and mice body weight and tumor volume were measured every Tuesday, Thursday and Sunday. The tumor volume (V) was calculated as (length×width²)/2.

At Day 23, mice were subject to euthanasia, from which tumors were collected, weighed and photographed. Mice body weights, tumor sizes and tumor weights were analyzed using the t-test in SPSS, and group differences were deemed statistically significant when the p-value was 0.05 or less. Tumor weight based tumor growth inhibition (TGI) and Zheng-Jun Jin's Q value were calculated.

TABLE 3 Dosing regimen Dose Group Test articles N (mg/kg) Dosing Regimen 1 vehicle 8 saline Oral administration, once per day 2 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, three times in total 3 Compound 6 8 15 Tail vein injection, once per day 4 Compound 6-1 8 15 Tail vein injection, once per day 5 Compound 6-2 8 15 Tail vein injection, once per day 6 Compound 6-3 8 15 Tail vein injection, once per day 7 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, three times in total Compound 6 15 Tail vein injection, once per day 8 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, three times in total Compound 6-1 15 Tail vein injection, once per day 9 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, three times in total Compound 6-2 15 Tail vein injection, once per day 10 Anti-m-PD-1 8 10 Intraperitoneal injection, once every five days, three times in total Compound 6-3 15 Tail vein injection, once per day

The average mice body weights and average tumor sizes from Day 9 to Day 23 in different groups were summarized in Table 4 and 5. The individual and group average tumor weights, TG and Zheng-Jun Jin's Q value on Day 23 were in Table 6 and 7.

The animals in the vehicle group looked vigorous, and animals in other groups were also found normal in physical condition and activity. As shown in Table 4, the mice in each group generally had their body weights increased from Day 9 to Day 23, partly due to the tumor growth. No statistically significant difference was found between the vehicle group and each administration group, between the anti-PD-1 group and each combination therapy group, between each compound and the corresponding combination group, or between the Compound 6 group and Compound 6-1, 6-2 or 6-3 group

TABLE 4 Average mice body weights in vehicle and administration groups Average body weight (g) Group Day 9 Day 10 Day 12 Day 14 Day 16 Day 18 Day 20 Day 22 Day 23 1 16.43 16.68 16.98 17.34 18.00 18.90 19.31 20.51 21.02 2 16.38 16.44 17.01 17.38 18.40 19.12 19.99 20.16 21.11 3 16.39 16.85 16.87 17.03 17.88 17.89 18.25 18.37 18.98 4 16.29 16.75 16.89 17.18 17.79 17.99 18.32 18.57 19.31 5 16.45 16.69 16.78 17.22 17.62 18.05 18.67 19.14 19.63 6 15.99 16.25 16.51 17.26 17.91 18.13 18.75 19.38 20.06 7 15.87 16.77 16.76 16.86 17.35 17.62 17.56 17.72 18.13 8 16.17 16.46 16.66 16.95 17.24 17.58 17.72 17.94 18.17 9 16.33 16.57 16.71 16.90 17.00 17.46 17.67 17.99 18.59 10 15.91 16.24 16.75 17.00 17.50 17.69 17.91 18.13 18.86

If the tumor weight was deducted, the average mice weights in these ten groups were 18.19 g, 18.16 g, 17.63 g, 17.77 g, 18.04 g, 18.16 g, 17.76 g, 17.27 g, 17.51 g and 17.67 g, respectively, at Day 23. It can be seen that the mice body weights in the vehicle, anti-in-PD-1, and Compound 6-3 groups seemed to be equally higher than those in other groups; and Compound 6, even at a lower dose, might still be toxic, and its combination therapy with anti-PD-1 did not have the toxicity increased.

TABLE 5 Average mice tumor sizes in vehicle and administration groups Average tumor size (mm³) Group Day 9 Day 10 Day 12 Day 14 Day 16 Day 18 Day 20 Day 22 Day 23 1 173.96 210.40 442.90 550.17 916.09 1310.74 1815.88 2296.23 2319.68 2 194.48 348.18 602.52 873.05 1226.32 1673.71 2235.65 2525.48 2698.41 3 163.24 220.45 367.43 494.61 666.40 770.93 955.40 1094.31 1071.65 4 171.59 257.64 367.95 550.08 677.06 780.61 972.02 1062.24 1179.61 5 196.37 278.84 391.83 570.64 698.18 805.13 974.34 1196.22 1334.63 6 162.03 282.00 417.93 527.17 718.27 828.07 1072.57 1334.48 1558.87 7 159.21 198.36 285.35 328.88 438.56 463.48 481.03 465.59 456.22 8 170.37 235.84 349.01 442.58 440.97 503.75 656.04 646.76 714.71 9 182.35 222.32 362.44 480.23 537.52 628.13 720.97 727.85 876.30 10 195.97 255.22 398.36 530.38 567.17 661.28 820.61 938.73 1064.07

According to Table 5, the four compounds, alone or with anti-PD-1, all inhibited tumor growth. Tumors kept growing till Day 23 in most groups, while tumor size began to decrease at Day 23 in the Compound 6 group, and at Day 22 in the anti-PD-1+Compound 6 group.

The tumor sizes on Day 23 were found not significantly different between the Compound 6 group and the Compound 6-1, 6-2 or 6-3 group, or between the Compound 6+anti-PD-1 group and the anti-PD-1+Compound 6-1 or the anti-PD-1+Compound 6-2 group. The combined use of Compound 6-1, 6-2 or 6-3 with the anti-PD-1 provided better anti-tumor effect compared to the anti-PD-1, Compound 6-1, 6-2 or 6-3 alone.

Especially, the tumors in the anti-PD-1+Compound 6 group started to grow slowly on Day 16 and to reduce in size since Day 22. The average tumor size of this group on Day 23 was significantly smaller than that in the Compound 6 group, the anti-PD-1+Compound 6-3 group, and the anti-PD-1 group.

The data in Table 6 showed anti-tumor effects of the four compounds, alone or with an anti-m-PD-1 antibody, as measured by tumor weights, and each combination therapy group offered obviously better effect than its corresponding compound alone group. Further, although no difference was found between the Compound 6 group and the Compound 6-1/6-2/6-3 group, the mice obviously had lighter tumors when treated by the anti-m-PD-1 plus Compound 6 as compared to the combination of the anti-m-PD-1 and Compound 6-1, Compound 6-2 or Compound 6-3. The anti-m-PD-1 antibody inhibited tumor growth in a few mice but not effective to most. In the anti-m-PD-1+Compound 6 group, the tumor almost vanished in three mice (Mouse no.: 2, 7 and 8), and the tumors in another two mice were quite small (Mouse no.: 3 and 6).

TABLE 6 Individual and group average mice tumor weights in vehicle and administration groups Tumor weight (g) Mouse Mouse Mouse Mouse Mouse Mouse Mouse Mouse Group no. 1 no. 2 no. 3 no. 4 no. 5 no. 6 no. 7 no. 8 Average 1 2.43 2.21 3.69 1.03 1.84 3.03 4.42 3.99 2.83 2 3.4 0.09 3.89 4.45 2.4 0.92 4.87 3.59 2.95 3 0.95 0.28 0.59 2.43 2.97 0.97 2.04 0.57 1.35 4 0.87 1.19 2.32 2.87 1.58 1.68 1.31 0.49 1.54 5 0.84 1.58 0.84 2.56 1.78 2.12 0.89 2.11 1.59 6 2.85 1.24 2.76 1.31 1.97 1.03 3.12 0.95 1.90 7 0.86 0.16 0.22 0.6 0.61 0.33 0.08 0.10 0.37 8 0.92 1.05 1.22 0.19 0.65 1.02 0.88 1.06 0.90 9 1.34 0.87 0.23 1.63 1.13 0.99 0.86 1.08 1.08 10 0.86 1.87 0.98 1.34 1.35 0.13 2.13 0.98 1.19

According to Table 7, all four compounds worked synergistically with the anti-m-PD-1, and the anti-m-PD-1+Compound 6 group had the highest TGI among groups.

TABLE 7 Tumor weight based TGI and Zheng-Jun Jin's Q value of control and administration groups Group Vehicle TGI (%) Anti-m-PD-1 −4.28 Com. 6 52.30 Com. 6-1 45.63 Com. 6-2 43.82 Com. 6-3 32.73 Group TGI (%) Q value Anti-m-PD-1 + Com. 6 86.93 1.73 Anti-m-PD-1 + Com. 6-1 69.13 1.60 Anti-m-PD-1 + Com. 6-2 64.09 1.55 Anti-m-PD-1 + Com. 6-3 56.54 1.89

The data above indicated that 1) Compound 6 provided a good anti-tumor effect at a lower dose when used in combination with an anti-PD-1 antibody, resulting in enhanced anti-tumor effect with equal or slightly lower toxicity; 2) Compounds derived from Compound 6 with modifications, i.e., Compound 6-1, Compound 6-2 and Compound 6-3 also worked with an anti-PD-1 antibody in a synergistic manner; and (3) Compounds derived from Compound 6 with modifications, when administered with an anti-PD-1 antibody, were less effective in tumor growth inhibition as compared to Compound 6.

Example 3. Combination Therapy in mPD-1^(−/−)mPD-L1^(−/−)hPD-1^(+/+)hPD-L1^(+/+) Transgenic Mouse Model

MC38 cells were maintained at 37° C. in 5% CO₂ in RPMI 1640 medium (10-040-CV, Corning cellgro) supplemented with 10% FBS (10270-106, GIBCO, Thermo Fisher Scientific), 100 U/ml penicillin and 100 U/ml streptomycin in 10-cm Petri dishes.

Female C₅₇BL/6-Pdcd1^(em1(hPDCD1)) Cd274^(em1(hPD-L1)/Smoc) mice, 20-25 g (Shanghai Model Organisms), were subcutaneously injected with about 3×10⁵ MC38 cells, respectively.

TABLE 8 Dosing regimen Group Test articles N Dose (mg/kg) Dosing Regimen 1 saline 8 n.a. Intraperitoneal injection, QD, Day 0-13 hIgG4 3 mg/kg Intraperitoneal injection, Q2D, Day 0, 2, 4, 6, 8, 10 2 Compound 6 8 8 mg/kg Intraperitoneal injection, QD, Day 0-13 hIgG4 3 mg/kg Intraperitoneal injection, Q2D, Day 0, 2, 4, 6, 8, 10 3 saline 8 n.a. Intraperitoneal injection, QD, Day 0-13 anti-PD-1 3 mg/kg Intraperitoneal injection, Q2D, Day 0, 2, 4, 6, 8, 10 4 Compound 6 8 8 mg/kg Intraperitoneal injection, QD, Day 0-13 anti-PD-1 3 mg/kg Intraperitoneal injection, Q2D, Day 0, 2, 4, 6, 8, 10 Q2D: every other day

When tumors grew to 50-70 mm³, these mice were randomly assigned to four groups, 8 mice per group, this day was designated as Day 0. From Day 0, the animals were administered with an anti-PD-1 antibody (Toripalimab, Shanghai Junshi Biosciences Co., Ltd. China) in saline at 40.0 mg/mL, an hIgG4 (Novoprotein, NovoPro Bioscience Inc.) in saline at 3.3 mg/mL, Compound 6 in saline at 8 mg/mL in combination with the anti-PD-1 antibody, and Compound 6 in combination with hIgG4, respectively, according to the dosing regimen shown in Table 8 above.

Mice were observed every day for their physical conditions and activities, and mice body weight and tumor volume were measured twice a week. The tumor volume (V) was calculated as (length×width²)/2.

Mice in Group 1 and Group 2 were subjected to euthanasia at Day 14, and those from Group 3 and Group 4 on Day 21, from which tumors were collected and photographed. Mice body weights and tumor sizes were analyzed using the t-test in SPSS, and group differences were deemed statistically significant when the p-value was 0.05 or less. TGI and Zheng-Jun Jin's Q value were calculated.

The animals in all groups looked vigorous, and no mouse was found dead during the experiment. The average mice body weights in different groups were shown in FIG. 4 . The group median and individual tumor volumes from Day 1 to Day 14 can be found in FIG. 5 and FIG. 6 , respectively. The individual tumor sizes in all groups on Day 14 were shown in FIG. 7 , and the tumors from Group 3 and Group 4 on Day 21 were displayed in FIG. 8 .

As shown in FIG. 4 , the mice in each group generally had their body weights increased from Day 1 to Day 14, partly due to the tumor growth. There was no significant difference among 4 groups, but the average weight in Group 2 tended to be higher.

According to FIG. 5 and FIG. 6 , most mice had their tumors grow from Day 1 to Day 14, with the tumor sizes of a few mice in Group 4 kept small. The median tumor volume in Group 2 was not different from that of Group 1, while the median tumor volume in Group 4 on Day 14 was lower than that of the other three groups, which was further demonstrated in FIG. 7 . All these indicated that Compound 6, when used in a dose that was too low to provide any anti-tumor activity in combination with hIgG1, was able to provide a good anti-tumor effect when combined with the anti-PD-1 antibody.

Further, as shown in FIG. 8 , the mice in Group 4 had smaller tumor sizes on Day 21 than those in Group 3.

The average tumor sizes on Day 0 and Day 14, and TGI on Day 14 were summarized in Table 9 below. The Zheng-Jun Jin's Q value calculated on TGI was 1.25.

TABLE 9 Tumor sizes and tumor growth inhibition rates P value (tumor size on D14 Average tumor size (mm³) TGI (%) compared to Group Day 0 Day 14 on D14 Group 1) 1 59.4 ± 0.8 1825.0 ± 380.3 — 2 60.4 ± 0.5 1905.8 ± 270.6 −5% 0.867 3 59.1 ± 0.4  792.1 ± 207.1 58% 0.032 4 59.1 ± 0.3  592.1 ± 175.8 70% 0.011

The data above suggested that Compound 6, even at a dose showing no anti-tumor effect alone, worked synergistically with an anti-PD-1 antibody.

Example 4. Combination Therapy in Transgenic Mouse Model

The test of Example 3 was repeated in the same transgenic mouse model using a lower dose of anti-PD-1 antibody, i.e., 2.5 mg/kg anti-PD-1, with some other minor modifications.

In particular, female C57BL/6-Pdcd1^(em1(hPDCD1)) Cd274^(em1(hPD-L1))/Smoc mice (Shanghai Model Organisms), 5-7 weeks old, were subcutaneously injected with about 3×10⁵ MC38 cells, respectively.

When tumors grew to 50-100 mm³, these mice were randomly assigned to four groups, 8 mice per group, this day was designated as Day 0. From Day 0, the animals were administered with an anti-PD-1 antibody (Toripalimab, Shanghai Junshi Biosciences Co., Ltd. China) in 5% GS (5% glucose solution) at 40 mg/mL, an hIgG4 (Novoprotein, NovoPro Bioscience Inc.) in 5% GS at 3.3 mg/mL, Compound 6 in 5% GS at 8 mg/mL in combination with the anti-PD-1 antibody, and Compound 6 in combination with hIgG4, respectively, according to the dosing regimen shown in Table 10 below.

Tumor size growth curves were obtained and shown in FIG. 9 . The TGIs for groups administered with Compound 6+hIgG4, anti-PD-1, and Compound 6+anti-PD-1 were 4.30%, 46.95% and 70.53%, respectively, and the Zheng-Jun Jin's Q value was 1.43.

The data and results were similar to those in Example 3. Compound 6, when used at a dose showing no anti-tumor effect alone, worked synergistically with an anti-PD-1 antibody

TABLE 10 Dosing regimen Dose Group Test articles N (mg/kg) Dosing Regimen 1 5% GS 8 n.a. Intraperitoneal injection, QD × 14 hIgG4 2.5 mg/kg Intraperitoneal injection, BIW × 3 2 Compound 6 8 8 mg/kg Intraperitoneal injection, QD × 14 hIgG4 2.5 mg/kg Intraperitoneal injection, BIW × 3 3 5% GS 8 n.a. Intraperitoneal injection, QD × 14 anti-PD-1 2.5 mg/kg Intraperitoneal injection, BIW × 3 4 Compound 6 8 8 mg/kg Intraperitoneal injection, QD × 14 anti-PD-1 2.5 mg/kg Intraperitoneal injection, BIW × 3 BIW: twice a week

Example 5. Combination of CHK Inhibitor, Anti-PD-1 Antibody and Gemcitabine had Synergic Anti-Tumor Effect

MC38 cells were maintained at 37° C. in 5% CO₂ in RPMI 1640 medium (10-040-CV, Corning cellgro) supplemented with 10% FBS (10270-106, GIBCO) and used before the 10th subculture.

Female C57BL/6-Pdcd1^(em(hPDCD1)) Cd274^(em1(hPD-L1)/Smoc) mice (Shanghai Model Organisms), 20-25 g, were subcutaneously injected with about 5×10⁵ MC38 cells, respectively.

When tumors grew to 50-70 mm³, these mice were randomly assigned to 8 groups, 8 mice per group, this day was at Day 9. From Day 9, the animals were administered with gemcitabine (GEM) in saline at 20 mg/mL, an anti-PD-1 antibody (Toripalimab, Shanghai Junshi Biosciences Co., Ltd. China) in saline at 40 mg/mL, Compound 6 in saline at 8 mg/mL, Compound 6+gemcitabine, gemcitabine+anti-PD-1, Compound 6+anti-PD-1, Compound 6+gemcitabine+anti-PD-1, and the control vehicle (5% GS), respectively, according to the dosing regimen shown in Table 11 below.

Mice were observed every day for their physical conditions and activities, and mice body weight and tumor volume were measured every other day. The tumor volume (V) was calculated as (length×width²)/2.

TABLE 11 Dosing regimen Dose Group Test articles N (mg/kg) Dosing Regimen 1 vehicle 8 n.a. IP, QD × 14 2 GEM 8 20 IV, QW × 2 3 anti-PD-1 8 10 IP, Q5D × 3 4 Compound 6 8 15 IP, QD × 14 5 Compound 6 8 15 IP, QD × 14 GEM 20 IV, QW × 2 6 GEM 8 20 IV, QW × 2 anti-PD-1 10 IP, Q5D × 3 7 Compound 6 8 15 IP, QD × 14 anti-PD-1 10 IP, Q5D × 3 8 Compound 6 8 15 IP, QD × 14 anti-PD-1 10 IP, Q5D × 3 GEM 20 IV, QW × 2 QW: every week; Q5D: every five days.

Mice body weights, and tumor sizes were analyzed using the t-test in SPSS, and group differences were deemed statistically significant when the p-value was 0.05 or less.

Tumor growth inhibition (TGI) was calculated by the following formula. Tumor growth inhibition=(average tumor size in vehicle group-average tumor size in administration group)/average tumor size in vehicle group×100%

Zheng-Jun Jin's Q value was calculated as described above.

The animals in the vehicle group looked vigorous, and no mouse was found dead in all groups during the experiment. The average tumor sizes from Day 9 to Day 23 in different groups were shown in FIG. 10 . It can be seen the mice in Group 1 to Group 4 generally had their tumor sizes increased from Day 9 to Day 23, while mice tumor sizes stopped increasing on Day 22 and afterwords in Group 5. The mice in Group 6 to Group 8 had tumor growth under control. The data suggested that the combination of Compound 6 with GEM, anti-PD-1, or both had better anti-tumor activities than the monotherapies and the GEM+anti-PD-1 combination. Among the three groups with best anti-tumor effects, the average tumor size in Group 8 was the smallest and significantly smaller than that of the other two groups, indicating the 3-drug combination's good efficacy.

TABLE 12 Tumor growth inhibition and Zheng-jun Jin's Q values Treatment E_(AB) E_(A) E_(B) Q value Compound 6 + GEM E_(compound 6+GEM) E_(compound 6) E_(GEM) 1.02 GEM + anti-PD-1 E_(GEM+PD-1) E_(GEM) E_(PD-1) 0.90 Compound 6 + anti-PD-1 E_(compound 6+PD-1) E_(compound 6) E_(PD-1) 1.33 Compound 6 + GEM + E_(compound 6+GEM+PD-1) E_(compound 6) E_(GEM+PD-1) 1.31 anti-PD-1* E_(compound 6+GEM+PD-1) E_(GEM) E_(compound 6+PD-1) 1.06 E_(compound 6+GEM+PD-1) E_(PD-1) E_(compound 6+GEM) 1.26 *As the limitation of the evaluation formula, the combination therapy of three compounds was evaluated by different permutation and combination.

Based on the tumor sizes on Day 23, TGIs of Group 2 to Group 8 were determined to be 30.02%, 17.05%, 52.53%, 67.75%, 37.74%, 80.83% and 92.22%, respectively.

The Zheng-Jun Jin's Q values were calculated and summarized in Table 12 above.

It can be seen that Compound 6 worked synergistically with the anti-PD-1 antibody, or the combination of the anti-PD-1 antibody and low dose gemcitabine, which was not observed in other combinations. 

1. A method for treating a cancer in a subject in need thereof, comprising administering a subject in need thereof an therapeutically effective amount of a compound of formula I or the pharmaceutically acceptable salt thereof, in combination with an immunotherapeutic agent or a therapeutic agent targeting a cancer-promoting molecule,

wherein Y is NH, O, S, or CH₂; R¹ is selected from the group consisting of

wherein X is CH₂, NH, S, or O, R⁸=—H, —NH₂, —OH, —N(R⁴R⁵), —C(R⁴R⁵)₁₋₇NR⁶R⁷, —C(R⁴R⁵)₁₋₇OR⁶, or —N(R⁴)NR⁵R⁶, wherein R⁴, R⁵, R⁶, and R⁷ are independently H, C₁-C₆ alkyl, C₃-C₈ cycloalkyl with or without nuclear heteroatoms such as O, S, and N; optionally substituted aryl, or optionally substituted heteroaromatic, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are independently H, C₁-C₆ alkyl, C₃-C₈ cycloalkyl with or without nuclear heteroatoms such as O, S or N; optionally substituted aryl, or optionally substituted heteroaromatic, R² is selected from a group consisting of H, OH, NH₂, OR¹⁴, NR¹⁴R¹⁵, alkyl, aryl, heteroaryl, cycloalkyl, arylalkyl, heterocyclyl, heterocyclylalkyl, alkenyl, and alkynyl, wherein R¹⁴ and R¹⁵ are independently H, C₁-C₆ alkyl, C₃-C₈ cycloalkyl with or without nuclear heteroatoms such as O, S, N; optionally substituted aryl, or optionally substituted heteroaromatic, and R³ is selected from a group consisting of H, alkyl, aryl, heteroaryl, cycloalkyl, arylalkyl, heterocyclyl, heterocyclylalkyl, alkenyl, and alkynyl.
 2. The method according to claim 2, wherein R³ is selected from the group consisting of

wherein R¹⁶, R¹⁷, and R¹⁸ are independently H; F, Cl, Br, I; C₃₋₈cycloalkyl of C₁-C₈alkyls, C₃-C₈ cycloalkyls, aryls, and heteroaryls; —OR¹⁹; —SR¹⁹; —NR¹⁹R²⁰; —S(O)R¹⁹; —S(O)₂R¹⁹; —S(O)₂NR¹⁹R²⁰; —C(O)NR¹⁹R²⁰; —N(R¹⁹)C(O)R²⁰; —N(R¹⁹)S(O)₂R²⁰; —N(R¹⁹)C(O)N(R²⁰R²¹); N(R¹⁹)C(O)OR²⁰; optionally substituted aryl, optionally substituted heteroaryl, optionally substituted aryalkyl, optionally substituted heterocyclyl, optionally substituted heteterocyclylalkyl; optionally substituted alkenyl, or optionally substituted alkynyl; where R¹⁹, R²⁰, and R²¹ are independently H, C₁-C₈ alkyl, C₃-C₈ cycloalkyl, optionally substituted aryl, optionally substituted alkylaryl, or optionally substituted heteroaryl, or R¹⁶, R¹⁷, and R²¹ are independently part of a fused ring containing 0-3 heteroatoms selected from N, O, and S.
 3. The method according to claim 1, wherein Y is NH.
 4. The method according to claim 1, wherein Y is O.
 5. The method according to claim 1, wherein Y is S.
 6. The method according to claim 1, wherein Y is CH₂.
 7. The method according to claim 1, wherein the compound of formula I is selected from the group consisting of 2-(4-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(2-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(2-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(S-3-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(R-3-piperidine-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-piperidine-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-piperidine-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxyli-c acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(2-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(S-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(R-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(2-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide 2-(4-chlorophenyl)-4-(4-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide 2-(4-chlorophenyl)-4-(S-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(R-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-bromophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(2-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(S-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(R-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(4-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-piperibine-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydrothiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydropyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-tetrahydrofuran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-tetrahydrothieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(2-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(S-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(R-3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-tetrahydropyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-α-pyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-α-thiapyran-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(2-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(4-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(S-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(R-3-pyridin-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyridin-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-thiapyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyran-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-bromophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(2-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(S-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(R-3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-pyrrol-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-thieno-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N-methyl-carboxylic acid amide, 2-(3-chlorophenyl)-4-(3-furan-amino)-thieno[2,3-d]pyridazine-7-N,N-dimethyl-carboxylic acid amide, 2-(4-fluorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-tetrahy dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-tetrahydropyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(2-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(4-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(S-3-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(R-3-piperidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno [2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiapyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahy dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahy dropyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-7-formamide; 2-(4-fluorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-tetrahy drofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(S-3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(R-3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolidinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrothiophenemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahydrofuranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl-formamide; 2-(4-chlorophenyl)-4-(3-tetrahy drofuranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl-formamide; 2-(4-fluorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-α-pyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-α-thiopyranmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(2-pyridinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(4-pyridinemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-pyridinemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; 2-(4-chlorophenyl)-4-(3-thiopyranylmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-thiopyranylmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; 2-(4-chlorophenyl)-4-(3-pyranmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-pyranmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; 2-(4-fluorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-furanmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-furanmethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-fluorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-bromophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(2-pyrrolemethyl)-thieno[2,3-d] pyridazinyl-7-formamide; 2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-pyrrolemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; 2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-thiaphenemethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; 2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]pyridazinyl-7-N-methyl formamide; 2-(4-chlorophenyl)-4-(3-furanmethyl)-thieno[2,3-d]pyridazinyl-7-N,N-dimethyl formamide; and 2-(3,5-dichlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide.
 8. The method according to claim 7, wherein the compound of formula I is selected from the group consisting of 2-(3-fluorophenyl)-4-(3-piperidineamino)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-piperidinyloxy)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, 2-(3-fluorophenyl)-4-(3-piperidinylthio)-thieno[2,3-d]pyridazine-7-carboxylic acid amide, and 2-(3,5-dichlorophenyl)-4-(3-piperidinemethyl)-thieno[2,3-d]pyridazinyl-7-formamide.
 9. The method according to claim 1, wherein the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting molecule is an inhibitor of PD-1, PD-L1, CTLA-4, HER-2, CD20, CD33, or CD52.
 10. The method according to claim 9, wherein the immunotherapeutic agent or the therapeutic agent targeting a cancer-promoting molecule is an antibody targeting PD-1, PD-L1, CTLA-4, HER-2, CD20, CD33, or CD52, or an antibody-drug conjugate (ADC) or a CAR-T cell targeting PD-L1, HER-2, CD20, CD33, and/or CD52.
 11. The method according to claim 10, wherein the antibody targeting PD-1 is selected from the group consisting of Nivolumab, Pembrolizumab and Toripalimab.
 12. The method according to claim 10, wherein the antibody targeting PD-L1 is selected from the group consisting of Atezolizumab, Druvalumab and Avelumab.
 13. The method according to claim 1, wherein the subject is further administered with a chemotherapeutic agent.
 14. The method according to claim 13, wherein the chemotherapeutic agent is selected from the group consisting of cisplatin, pemetrexed, gemcitabine, cytarabine, hydroxycarbamide, temozolomide, irinotecan, cyclophosphamide, mitoxantrone, etoposide, folinic acid, fludarabine, and fluorouracil.
 15. The method according to claim 1, wherein the cancer is a solid cancer selected from the group consisting of lung, prostate, ovarian, brain, breast, skin, bladder, colon, gastrointestinal, head and neck, gastric, pancreas, neurologic, renal, and liver cancer.
 16. The method according to claim 1, wherein the cancer is a hematological cancer selected from the group consisting of lymphocytic leukemia, myeloid leukemia, non-Hodgkin lymphoma, and Hodgkin lymphoma. 